A.Eric Borden, owner of ESB
Contracting in Forked River, N.J., responds:
Clipped-head nails are collated at a steeper angle
than round-head nails. The steeper collation angle
provides two main advantages: There are more nails
in a stick, and the working clearance (the angle
between the gun and the work) is greatly
improved.
The model building codes do not require the use
of round-head nails. The codes specify nails by
length and by shank diameter, not by the type of
nail head. Lateral load capacity depends on a nail
shaft’s shear strength, and withdrawal
resistance depends on shank type. An increase in
withdrawal resistance can be achieved by using a
screw-shank or ring-shank nail.
The industry reference for evaluating pneumatic
nails is the National Evaluation Report
(NER-272), which is posted at the SENCO Web site
(www.senco.com/pdf/facts/ner272.pdf). This report
lists the nailing schedules for pneumatic fasteners
for all of the model building codes (BOCA, CABO,
SBCCI, and ICBO).
A panel’s shear strength depends more
on the depth to which fasteners are driven than on
the shape of the nail head. Nail heads should be
set flush with the surface of the sheathing, not
countersunk. When fasteners are driven through the
outer ply of plywood or OSB, shear strength
decreases significantly. But if the nails are
properly driven, there is no difference in
performance between the two types of nail heads,
because the pull-through values of both nails
exceed the performance requirements for the
assembly. Of course, regardless of the type used,
proper spacing of the nails is essential.
Although there is no evidence that round-head
nails provide greater shear strength or withdrawal
resistance than clipped-head nails, some building
inspectors ignore the facts and require round-head
nails on exterior sheathing. These inspectors
reason that the larger head area of round-head
nails reduces the likelihood of overdrive.
Currently, all manufacturers make separate
nailers for the two types of nail heads, and the
nails are not interchangeable. Nails with a third
type of head, the offset round head, are available
from Paslode, Senco, and Hitachi. These nails can
be used in clipped-head guns. For more information,
see "Choosing Collated Nails," 6/00.